Aviation trainer



K. A. KAIL AVIATION TRAINER June 6, 1950 7 Sheets-Sheet 1 Filed May 28. 1946 FIG.

KARL A. KAIL INVENTOR. y fw ff/ 4770 Mfrs K. A. KAM.

AVIATION TRAINER June 6, 1950 7 Sheets-Sheet 2 Filed May 28, 1946 KARL A- KA| INVENTOR ATTO R N EY K. A. KAlL AVIATION TRAINER June 6, 1950 7 Sheets-Sheet 3 Filed May 28. vi946 vlwi WI m

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INVENTOR ATTORNEY June 6, 1950 K. A. KAu. 2,510,578

AVIATION TRAINER Filed May 28, 1946 '7 Sheets-$11961'l 4 220 A' z/a /64 Q MVN l W z/z 208 20@ 202 ma /W /az KARIL. A. KAIL NVENTOR ATTO R N EY June 6, 1950 K. A. KAII. 2,510,578

AVIATION TRAINER Filed May 28, 1946 7 Sheets-Sheet 5 KARL. A KAIL INVENTOR TTORNEY K. A. KAlL.

AVIATION TRAINER June 6, 1950 7 Sheets-Sheet 6 Filed May 28. i946 FIG. I9

Mw. n .m/ m A@ Mw m Lm mm K. A. KAlL AVIATION TRAINER June 6, 1950 Filed May 28, 1946 lNvr-:NToR

ATTORNEY KARL A. KAI L l zaag zaga. fr

Patented June 6, 1950 2,510,578 AVIATION TRAINER Karl A. Kail, Montrose, Pa., assignor to Link Aviation, Inc., Binghamton, N. Y., a corporation of New York Application May 28, 1946, Serial N o. 672,875

4 Claims.

This invention relates to improvements in grounded aviation trainers, and more particularly in altitude systems therefor, which systems are employed to cause the altimeter and vertical speed indicator in the trainer to operate in a manner closely simulating the operation of the altimeter and vertical speed indicator of a real plane in actual flight.

Trainers of the type with which my invention may be used are disclosed in U. S. Patents 1,825,462 and 2,099,857 issued to Edwin A. LinkI and the improvements of this application will be disclosed in connection with improvements covered by my application Serial Number 619,361 filed September 29, 1945 for Aviation trainer, which application also discloses trainers of the type covered by the same U. S. patents. This application has matured into Patent No. 2,485,292, dated Oct. 18, 1949. Such trainers are known by those skilled in the art to include a fuselage rotatably mounted with respect to a stationary base by means of a main spindle, the fuselage also being universally mounted upon the top of the spindle. Within the trainer is provided a pair of rudder pedals and a control wheel or stick, and the manual controls Within the trainer are connected to suitable vacuum-operated apparatus so that the fuselage turns, dives, and banks in response to the movements of the manual controls in the same manner that a plane in actual flight turns, dives, and banks in response to movements of the corresponding controls in the plane.

Also in trainers of the type being considered,

there are provided instruments Which simulate the instruments of `a, real plan'e, these instruments including an airspeed indicator, an altimeter and a vertical speed indicator. Also within the fuselage is a lever which simulates the throttle control lever of a real plane. Upon a manipulation of the throttle control simulating lever in the trainer, the airspeed indicator, altimeter and vertical speed indicator respond generally in the same manner that the real instruments in a plane in actual flight would respond to a corresponding movement of the throttle control lever in the plane. Also, these three instruments respond to a change in the diving or climbing attitude of the fuselage (hereinafter referred to as pitch) in the same manner that the instruments in a real plane would respond to corresponding changes in the attitude of the plane.

Insofar as the altitude systems in the prior art trainers responsive to the movement of thethrottle lever and changes in pitch attitude oi the trainer are concerned, these systems have conventionally included a vacuum system comprising a tank connected through a pair of valves known as the climb-dive valves to a source of reduced pressure and to the atmosphere. The climb-dive valves have been operated in response to movements of the lever and to changes in the pitch attitude of the fuselage in order that the pressure within the altitude tank would be selectively varied. An altimeter and a vertical speed indicator have been `connected to the tank, and responsive to the pressure therewithin, so that they indicate the assumed altitude and assumed vertical speed of the trainer. Such well known vacuum-operated altitude systems have had several defects long known to the prior art which my invention aims to correct. For example, in transferring the changes in pressure within the tank to the altimeter and vertical speed indicator, it has been necessary to use a diaphragm which would expand or contract in response to such changes in pressure. The disphragm in turn has been connected to certain mechanical linkage which in turn operates a selsyn-type 'transmitting system which actuates the instruments in question. Upon a change in pressure Within the tank, and especially in the case where the direction oi change in pressure Within the tank is reversed, a denite dead-spot in the diaphragm and in the linkage is present. Accordingly, there is lost motion and the instruments have also reflected this dead spot, thereby giving faulty indications.

Also in the case of the climb-dive valves it has been found impossible to adjust these valves near the zero vertical speed position in order that slight movements of the throttle lever or changes in attitude of the plane would result in changes in instrument indication.

Also, in previously known trainers the limitations of the altitude systems have rendered it diicult to achieve high assumed altitudes.

Another important disadvantage of the previously used vacuum operated altimeter and vertical speed systems Was that it was necessary to calibrate each altimeter and vertical speed indicator used in the trainers over the entire range of instrument indication because of the impossibility of manufacturing diaphragms which would all respond exactly the same amount to any given change in pressure within the tank at any level of pressure within the tank. (The same is lalso true of all aircraft altimeters and vertical speed indicators, which, as is well known, are diaphragm operated.)

Also, in previously known trainers the instruments of the trainer have not been directly nor realistically affected by the rough air means in the trainer.

It is, therefore, a general object of my invention to provide a, new altitude system for use in grounded aviation trainers, which system will eliminate the previously described disadvantages.

It is a more particular object of my invention to provide an altitude system whereby a sensitive zero may be obtained and whereby changes in the assumed direction of vertical movement of the trainer will not produce dead spots in the functioning of the apparatus.

It is another important advantage of my invention to provide an altitude system wherein it will not be necessary to calibrate all of the altimeters and vertical speed indicators throughout their entire range.

It is still another object of my invention to provide means whereby the indications of the vertical speed indicator and altimeter will be affected by simulated rough air means, in the same manner that the corresponding instruments of a. real plane are aiected by rough air conditions.

Another object of my invention is to provide means whereby an unlimited high assumed altitude may be obtained.

Other important objects of my invention will be made more clear as the description proceeds.

In order that the preferred disclosed embodiment of my invention may be clearly understood, reference is made to the accompanying drawings wherein,

Fig. 1 is a general perspective view oftrainers of the type disclosed in the above mentioned U. S. patents, and showing the general location of the important parts of my invention.

Fig. 2 is a perspective view showing the previously mentioned universal joint, and the pitch action take-o apparatus of such trainers.

Fig. 3 is a general perspective view showing the general relationship of certain of the control systems in such trainers, as disclosed in Patent Number 2,485,292, and how my invention may be associated therewith in order to form a completely operable apparatus.

Fig. 4 is a perspective View of the engine power amplifier which may be used in conjunction with my invention.

Fig. 5 is a detailed perspective view of a portion of the apparatus shown in Fig. 4.

Fig. 6 is a cross-sectional view of one of the control valves which may be used in conjunction with my invention.

Fig. 7 is a perspective View of the air speed control valve.

Fig. 8 is a perspective view of the air speed power amplifier.

Fig. 9 is a detailed perspective view of one of the leverage systems which may be incorporated in trainers of the type being considered.

Fig. 10 is a perspective view of the altitude unit of this invention.

Fig. 11 is a front view of a typical vertical speed indicator.

Fig. 12 is a wiring diagram of the motors shown in Fig. 10.

Fig. 13 is a general perspective view of the rough air apparatus which may be combined with my invention.

Figs. 14, 15, 16, 17, 18 and 19 are views of different parts of the apparatus shown in Fig. 13.

Referring now to Fig. 1, it will be seen that the illustrative training device includes a base I0 which rests upon the floor of the room in which the training device is housed. The fuselage I2 is positioned above the base, and in the fuselage is a seat' |40. for the student. Referring also to Fig. 2, it will be seen that the bottom of the fuselage is designated I2a., and rests upon the supporting plate 260 to which it is suitably attached, as by bolts. Plate 260 is integral with the upper member 262 of the universal joint which is designated generally I4. The gimbal ring of the universal joint is numbered 264, and this universal joint is supported by the ears I8 (only one shown) which are integral with the pedestal 20. Pedestal 2|) is bolted to the cross-arms 22 by bolts 24, and these cross-arms are aflixed to the Octagon 26. The cross-arms 22, pedestal 20 and all elements supported thereby are mounted upon the top of the main spindle 28 which is suitably rotatably mounted with respect to the stationary base I0. The universal joint I4 is arranged so that the fuselage I2 may pitch about a transverse axis coincident with the axes of the pins 266, as well as about an axis perpendicular to this firstaxis. Four collapsible-expansible bellows 30, 32, 34 and 36 are provided, these bellows being, respectively, the front and rear pitching bellows and the left and right banking bellows. The upper end of each of these bellows is suitably affixed to the bottom I2a of fuselage I2, while the bottom end of each of these bellows is suitably affixed to a different one of the crossarms 22.

The two supporting members 38 are suitably carried by the forward cross-arm 22, and these supporting members in turn carry the conventional turning motor 40. Within fuselage I2 are placed a pair of rudder pedals 42 ahead of the seat I4a, as well as a control wheel 44 which is supported by shaft 45 which in turn is rotatably and slidably supported by the pedestal 46 positioned in front of the instrument panel 48. As is well known to those skilled in the art, and also as disclosed in the above mentioned patents and application, the rudder pedals 42 control the turning motor 40 which in turn rotates the fuselage I2, all of the apparatus shown in Fig. 2, as well as the bellows, Octagon, and the turning motor itself, to the right or left depending on which rudder pedal is pressed forward. In this manner, the student may cause the fuselage I2 to rotate in simulation of the turning of a plane in actual flight. The turn indicating instruments conventionally placed upon the instrument panel 48 respond accordingly. Upon a rotation of the control wheel 44 counterclockwise, the left banking bellows 34 is collapsed and the right banking bellows 3B is expanded, resulting in a banking of fuselage I2 to the left. An opposite rotation of control wheel 40 results in a collapsing of bellows 36 and an expansion of bellows 34, and fuselage I2 banks to the right. At the same time, a pushing ahead of the control wheel 44 causes bellows 30 to collapse and bellows 32 to expand, so that fuselage I2 assumes a nose-down position. On the other hand, a pulling to the rear of control wheel 44 results in a collapsing of bellows 32 and an expansion of bellows 30, and fuselage I2 assumes a more nose-up position. Accordingly, the fuselage I2 may be turned, banked, and dived and climbed in the same manner that a plane in actual night is controlled by the pilot. All of the instruments upon panel 48 respond properly to any given movement offuselagel2 or to any combination of such movements.

A plurality of inspection ports 50 are carried by the side of fuselage I2 in order that they may be removed for inspection of the apparatus contained therein.

Steps 52 are provided for easy access and egress to and from fuselage I2, and door 54 may be closed and opened as the occasion requires. A slidable hood 56 is mounted upon the top of fuselage |2, and this hood may be moved to the rear of the position shown in Fig. 1 to completely enclose the student in fuselage I2 in order that instrument flying conditions may be accurately imitated.

In order that the use of the apparatus of this invention may be completely understood and illustrated in connection with the apparatus disclosed in the above mentioned patents and application, the following sequence of presentation will be adopted:

1. Throttle control lever setting and altitude will be combined to produce the factor of assumed engine power output or assumed manifold pressure, which for the purposes of this application, may be considered to be equivalents.

2. Engine power output will be combined with the factor of fuselage attitude to produce the factor of assumed air speed.

3. Assumed air speed will be combined with the factor of fuselage attitude to produce the factor of assumed vertical speed. i

4. Assumed vertical speed will be integrated with respect to time in order to produce the factor of assumed altitude.

Then, the effect of the rough air mechanism which may be incorporated in trainers of the type being considered will be combined with my improved apparatus in order to further simulate accurate flying conditions.

Means for producing the factor of assumed engine power output Reference is now made to Fig. 3 where the throttle lever is designated |00. Lever is pivotally mounted upon the rod |02 which is afxed inside the fuselage I2 in a proper position relative to the Seat |4a. .Integral with the throttle lever |00 is the arm |04 to which is pivotally attached the upper end of vertical link Pivotally attached to the lower end of link |06 is the link |08, the other end of which is also pivotally attached to the fore end of bell crank ||0 which is pivotally mounted upon the rod ||2 affixed within the interior left side of fuselage I2. To the lower end of bell crank 0 is pivotally attached the forward end of link H4.: It will be seen that the rear end of link ||4 is pivotally attached to the upper end of arm ||6 which is a part of the engine power or manifold pressure engine unit designated generally by ||8.

Reference is now made to Fig. 4 which is a detailed disclosure of the construction of the manifold pressure engine unit designated generally by ||8. In Fig. 4 the rear end of the link ||4 which is moved by the throttle lever is shown, as is the arm |6. It will be seen that the block |20 is integral with the arm ||6 and that block |20 is rotatably mounted upon rod |22 which is fixedly held in the frame |24. Frame |24 is rigidly attached to the bottom |2a of the fuselage I2. Two shafts |26 and |28 are rotatably mounted in the block |20. Upon the outer end of the shaft |26 is mounted the spur gear |30 while upon the outer ends of the shaft |28 are mounted the spur gears |32 and |34. Meshing with gear |30 is the spur gear |36 which is afixed to the large spur gear |38 which is rotatably mounted upon shaft |22. Gear |38 is driven by the shaft |40 splined at |40a and which in turn is driven by motor |42.

A suitable reduction gear train may be interposed between the motor |42 and the spline |40a.

Still referring to Fig. 4, rotatably mounted upon the fixed rod |22 and driven by .gear |34 is the spur gear |44 which is aixed to the insulating ring |46 to rotate the same. Aixed to the insulating ring |46 are the two split contact segments |48 and |50. Considering now Fig. 5 in conjunction with Fig. 4, it will be seen that the insulating disc |46 carries the split contact segments |48 and |50 by means of rivets |5I. Rotatably mounted upon the xed rod |22 is the drum |52 carrying the contact |54. A string |56 has its forward end wound around the drum |52 and attached thereto, while the rear end of this string is attached to the spring |58 which has its rear end attached to the arm |60, which in turn is attached to the gear sector |66.

Integral with the drum |52 is the gear |62 which is positioned by the `gear sector |64. The gear sector |64 is pivotally mounted upon the circular block |66 integral with the rod |68 which is affixed in frame |24. Spring |58 and string |56 bias drum |52 to remove the backlash between gear |62 and sector |64. A second spring |61 is affixed to the fixed member as shown, and aflixed to the spring is the string |69 which winds around and is anchored to the drum |10 which is affixed to the contact segments |48 and |50. This spring and string arrangement biases the segments |48 and |50 to remove the backlash between these segments and motor |42.

A pair of contacts |12 and |14 are carried by the insulating members |16 in turn held by frame |24 so as to engage the contact segments |40 and |50 as better seen in Fig. 5. Each of the contacts |12 and |14 is connected to motor |42 by one of the conductors |18 and |80, and the contact |54 is grounded. Motor |42 is of the type that when contact |54 is in engagement with both of the contact segments |48 and |50 the motor is deenergized. When the contact |42 engages only the contact segment |48, motor |42 is energized to turn in one direction, and when contact |54 engages only the other contact |50, motor 42 is energized to turn in the opposite direction.

Assuming that the contact |54 is engaging both of the contact segments |48 and |50, the :motor |42 will be at rest. Lf the throttle lever |00 is then pushed ahead, i. e., that is to the left in Fig. 3, the link |06 moves upwardly with the movement of the throttle lever. The upward movement of link |06 results in a movement ahead of link ||4, and referring to Fig. 4 the arm ||6 and block |20 are rotated counterclockwise about the rod |22. Accordingly, gears |30, |32 and |34 and shafts |26 and |28 are likewise rotated counterclockwise about rod |22. Gear |36 remains stationary, and the coa:ction of gears |30 and |36 results in a rotation of the gear |30 upon the shaft |26, and consequently, the gears |32 and |34 are rotated resulting in -a rotation of the gear |4'4 which is fixed to the insulating block |46. The rotation of gear 44 results in a countenclock-wise rotation of the insulating block |46 and contact segments |48 and |50.

The counterclockwise rotation of the contact segments 48 and |50 will disengage the contact |54 from engagement with the :contact segment |50 and the contact |54 will engage only segment |48. As a result motor |42 will be energized so that the shaft |40 rotates clockwise as seen from the left. The running of motor |4'2 will result in a rotation of the gears |38, |36, |30, |32, |34 and |44, and the rotation of gear |44 will rotate the insulating disc |46 and contact segments |48 and |50 clockwise. The motor |42 will continue to run until it has rotated the contact segments |48 and |50 through the same angle but in the opposite direction from which they were rotated as a result of the movement of the throttle lever and link ||4. When the contact segments |48 and |50 have been rotated through this angle, the Contact |54' will again engage both of the contact segments and motor |42 will stop. On the other hand, assuming that the -contact |54 engages both of the contact segments |48 and |50, if the throttle lever is moved to the rear, link |06 moves downwardly and link 4 moves toward the rear of the trainer. Arm ||6 is rotated clockwise as is block |20 and the movement of block |20 carries with it the shafts |26 and |28 and the gears |30, |32 and |34. The coaction of gear |30 with gear |30` which remains stationary results in a rotation of gear |30 and the rotation of this gear is imparted to the gear |44. The rotation of gear |44 is in a clockwise direction and the contact segments |48 and |50 move therewith. Contact |54 will become disengaged `from segment |48 but will remain in engagement with segment |50. The motor |42 is as a result energized and the splined shaft |40a is rotated in a counterclockwise direction. The running of motor |42 through the gears |38, |36, |30, |32, |34 and |44 results in a counterclockwise rotation of the split contact segments |48 and |50. The running of the motor continues until these two contact segments again are both in engagement with the contact |54. At this point motor |42 stops.

It will therefore be appreciated that the direction and magnitude of the output of motor |42 is dependent upon the setting of throttle lever |00 and consequently the angular position olf shaft |40 with respect to a predetermined Zero position is dependent upon the position of throttle lever |00. Accordingly, the angular position of shaft |40 with respect to an initial zero position may be taken as a measure of assumed engine ypower output or assumed manifold pressure, and this factor is responsive to changes in the setting of the throttle lever.

The second factor which is combined with throttle lever position to produce assumed engine power output (manifold pressure) is the factor of assumed altitude. As assumed altitude increases, assumed engine power decreases. In Fig. 3 the arrn |96 is shown, and, as will -be later more fully explained, this arm is always positioned in accordance with the factor off assumed altitude-the higher the assumed altitude the more counter-clockwise position arm |96 assumes. The arm |96 is affixed upon the right end of shaft |92 which controls the altitude valve designated generally by |84'.

Referring now to Fig. 6, it will be seen that valve |84 comprises a main body portion |86 having integral therewith an extension |88 which is threaded in a tapered fashion upon its outside and is also interiorly threaded. Lock nut |90 is provided. The stem of the valve is designated |92 and integral with this stem are the 8 threads |94 which lcoact with the threads within extension |88. The operating arm |96 is shown i'lxedly attached to the outer end of stem |92.

Integral with the stem |92 is the needle |98, tapered as shown. The plug 200 holds the seat 202 of the valve in place, plug 200 being hollow to permit the passage of vacuum therethrough, the chamber |99 in the valve being yconnected to the pump 20| through line 224. The capillary and bleed hole fitting assembly comprises a main body portion 204 having integral therewith the threaded extension 206 which fits inside the interiorly threaded left end of the main body portion |86. The body portion 204 is drilled at 208 to permit the passage of vacuum therethrough and the capillary 2 0 connects the drilled portion 208 `with the exterior fitting 2|2 which is connected with the Sylphon bellows 222 of the manifold pressure engine unit |8 through the vacuum line 2|4, as seen in Fig. 3. Bleed hole 2|6 connects the capillary 2|0 at all times with the atmosphere through the cup 2|8 which is filled with a suitable straining material 220, such as cotton. Sylphon bellows 222 is airtight in construction and therefore by changing the pressure within this bellows it may be made to expand or contract.

Referring now to Figs. 3 and 6, it will be appreciated that atmosphere enters the Sylphon bellows 222 at al1 times by virtue of the bleed hole 2|6. In the absence of other controlling factors, therefore, the pressure within bellows 222 would at all times be equal to the atmospheric pressure. However it will be appreciated that the position of needle |98 relative to seat 202 depends upon the position of the operating arm |96 which in turn depends upon the factor of assumed altitude. When arm |96 is positioned so that the valve formed by needle |98 and seat 202 is closed, valve |84 has no effect upon the Sylphon bellows 222. The valve may be adjusted to be closed when assumed altitude is zero. However, as the factor of assumed altitude increases, the operating arm 96 is rotated counterclockwise as seen in Fig. 3, and referring to Fig. 6 it will be seen that the needle |98 will be removed from the seat 202 by an amount depending upon the increase in assumed altitude. Vacuum will therefore be admitted through the line 224, through the needle valve and capillary 2|0 and connection 2|4 to the Sylphon bellows 222. The Sylphon bellows 222 will therefore be contracted by an amount dependent upon the setting of the instant assumed altitude. On the other hand, should the Sylphon bellows 222 be previously contracted a given amount 'as the result of an assumed altitude of a given amount, and thereafter the factor of assumed altitude is decreased, the valve |84 will be proportionately closed, a decrease in the application of vacuum to the interior of Sylphon bellows 222 results, and an expansion of the bellows 222 occurs. It will therefore be appreciated that the expansion and contraction of the Sylphon bellows 222 may be used as a measure of changes in the assumed manifold pressure or assumed engine power output insofar as these factors are dependent upon assumed altitude.

Bearing in mind the earlier detailed construction of the engine unit shown in Fig. 4, it will be appreciated that whenever the bellows 222 is collapsed, as may occur with an increase in assumed altitude the link 230 which has its lower end pivotally attached to the top of bellows 222 will be moved downwardly and inasmuch as the upper end of this link is pivotally connected to the rear end of sector |64, the rear end of sector |64 will also move downwardly, sector |64 pivoting upon the boss |66 integral with the shaft |68 fixed in the frame |24 of the unit. The fore end of sector |64 will move upwardly, and drum |52 will be rotated counterclockwise and the contact 54 will be moved in the same direction and out of engagement with contact segment |48. Motor |42 will therefore be energized in such a direction that the output shaft |40 is rotated counterclockwise. The counterclockwise rotation of the o-utput shaft |40 will result in a counterclockwise rotation of the contact segments |48, |50 and motor |42 will continue this rotation until both of the contact segments |48l and |50 are again engaged by the contact |54. At this instant motor 42 will stop. It will be appreciated that the angular rotation of the output shaft |40 will be dependent upon the 4extent of the collapsing of the Sylphon bellows 222 which is dependent upon the magnitude of the change in assumed altitude.

It should be noted that whenever the throttle vlever shown in Fig. 3 is moved to the rear,

the output shaft |40 is rotated counterclockwise by motor 42, and that when the Sylphon bellows 222 is collapsed as a result of an increase in assumed altitude, the output shaft |40 also rotates counterclockwise. It will thereforebe appreciated that the output shaft |40 is always rotated counterclockwise by the motor 42 in response to a positioning to the rear of the throttle lever |00 and/or by an increase in assumed altitude. Accordingly, the shaft |40 is rotated counterclockwise through an angle proportional to decreases in the assumed manifold pressure.

On the other hand, should the Sylphon bellows 222 be expanded as 'a result of a decrease in the assumed altitude of the trainer, it will be appreciated without a detailed explanation, that the contact segment 54 will be rotated clockwise and that the motor |42 will be energized to rotate the shaft 40 in a clockwise direction until the two contact segments |48 and |50 again both engage the contact |54. The angular rotation of shaft |40 in this direction will depend upon the amount of expansionof the bellows 222 which will depend upon the magnitude of the decrease in assumed altitude. It will be recalled that the output shaft |40 is also rotated clockwise in response to a forward movement of the throttle lever |00. Acordingly, the output shaft |40 is always rotated clockwise through an angle proportional to increases in the assumed manifold pressure, and the instant assumed manifold pressure may always be measured by the angular position of shaft 40 relative to a predetermined neutral position.

Parenthetically, at this point it should be noted that a notch |48a is placed in contact segment |48 seen in Fig. 5. In the operation of the unit in question the Contact segments |48 and |50 are never rotated in response to a' movement of the throttle lever so far as to move notch |48a opposite the contact |14. Notch |48a is therefore provided to limit the clockwise rotation of the contact segments when motor |42 is energized as a result of the clockwise rotation of contact |54 caused by an expansion of bellows 222. When contact |14 is opposite notch |48a, motor |42 will not run to rotatethe contact segments further clockwise.

Still referring to Fig. 4, it will be seen that the gear 234 is arranged to be krotated by the shaft |40, gear 234 being xedly mounted upon the shaft 236 which is rotatably mounted in the frame |24 of the unit I8. Upon the left end of shaft 236 is mounted the arm 238 to which is pivotally connected the rear end of link 240. Reference is now made to Fig. 3 where the link 240 is shown to have its fore end pivotally connected to the pitch action walking beam 242 which is pivotally mounted upon the shaft 244, the right end of which is rigidly held by the arm 246. To the lower end of the pitch action walking beam 242 is pivotally connected the link 248, the rear end of which is pivotally connected to the operating arm 250 of the air speed valve designated generally by 252.

By virtue of the just explained arrangement, it will be clear that the link 240 is always positioned according to the angular position of shaft |40 which, as explained, is a measure of the instant assumed manifold pressure or engine power output. An increase in assumed manifold pressure moves link 240 to the rear while adecrease moves it ahead. f

Parenthetically, in Figs. 3 and 4 it will be seen that the gear I38a, drives gear |3813` which is aixed upon the input shaft of the Selsyn-type transmitter |38e which is connected by electrical cable |38d to a Selsyn-type receiver |38e forming a part of the simulated manifold pressure indicator |38f mounted upon the instrument panel 48 in Fig. 1. As is Well known to the prior art,V indicator |38f comprises a needle |38g mounted upon the output shaft of the Selsyntype receiver |38e andV arranged to move over a dial |3811. graduated in terms of manifold pres-- sure to indicate the assumed manifold pressure. As will be understood by those skilled in theart, the output shaft of the receiver always positions the needle in accordance with the position of the input shaft of the transmitter which in turn is positioned by gear |38a. Inasmuch as gear |38a is always positioned by motor |42 which positions shaft |40 according to the assumed manifold pressure, it is clear that the indicator |38e always indicates tothe student the instant vassumed manifold pressure.

Means for combining the factor of assumed engine power with the pitch, attitude of the fuselage to produce assumed air speed Means will now be described for introducing the factor of climbing and diving movements (pitching) of the fuselage and combining this factor with the assumed engine power to produce assumed air speed.

Means for introducing the factor of climbing 'and diving of the fuselage l2 arey shown in detail in Fig. 2, to which reference is now made. In Fig. 2 the fuselage floor is designated |2a and it will be recalled that this floor rests upon the plate 260 which is attached to the .upper yoke 262 of the universal joint 4. The gimbal ring of universal joint I4 is designated 264, this gimbal ring being free to rock about the axis of pins 266, pedestal 20 holding ring 264. Yoke 2,62 is free to rock about an axis through ring 264 at right angles to the axis 266. The axes of pins 266 extend transversely of the fuselage I2 and are the axes about which the fuselage moves whenever its climbing or diving attitude is changed. Afxed to the yoke 262 is the rearwardly extending rod 268 upon which is movably mounted the carriage 210 which is provided with rollers 212 for easy movement therealong. The link 2`|4 is pivotally connected .to the pedestal 20,

as shown, and the upper end of this link is pivotally connected to the carriage 210.

v The upper end of carriage 210 is slotted as shown, and within this slot is the stud 216 which is alxed to the pitch action sector 218. The upper end of sector 218 is affixed to the transverse shaft 280 which is rotatably held by suitable brackets aixed to the floor I2a. Whenever the fuselage I2 assumes a diving attitude, it will be appreciated that the rear end of rod 268 is moved upwardly and that the carriage 210 moves toward the head of the fuselage. The lower end of sector 218 is moved ahead and the shaft 280 is rotated clockwise. On the other hand, whenever the fuselage I2 assumes a climbing attitude, the carriage 210 moves to the rear of rod 268 and the shaft 280 is rotated counterclockwise.

Referring now to Fig. 3, it will be seen that xedly mounted upon the left end of shaft 280 is the arm 246, to which reference has been previously made. When the fuselage I2 assumes a diving attitude, the arm '246 is rotated clockwise as seen in Fig. 3 and the rod 244 carried thereby is moved toward the rear. The pitch action walking beam 242 will be pivoted about the point at which link 240 is attached thereto, and consequently the lower end of beam 242 will move toward the rear of the fuselage. Link 248 moves in the same direction.

On the other hand, should the fuselage I2 assume a climbing attitude, arm l246 will be rotated counterclockwise as seen in Fig. 3. Shaft 244 will be moved ahead and pitch action walking beam 242 will be pivoted about the point at which link 240 is attached thereto. The lower end of walking beam 242 will be moved ahead, as will the link 248.

It will be recalled link 240 moves ahead in response to a decrease in assumed engine power output. Accordingly, link 248 moves to the rear. Increases in assumed engine power reverse the directions of movements of links 240 and 248.

It will therefore be appreciated that the pitch action walking beam 242 differentially combines the two factors of assumed engine power and climbing and diving attitude of the fuselage and that it positions link 248 in accordance with these two factors. In the case of a plane in actual flight an increase in engine power as well as a diving of the plane results in an increase in air speed. Decreases in engine power and climbing of the plane result in lower air speed. It should be noted that whenever an increase in the assumed engine power occurs or when the fuselage I 2 is placed in a diving position, the link 248 moves to the rear. Also, when a decrease in the assumed engine power or a climbing attitude of the fuselage I2 occurs, link 248 moves ahead. Consequently, the position of link 248 may be taken as a measure of the assumed air speed. The farther to the rear link 248 is positioned, the higher is the assumed air speed.

Reference is now made to Fig. 'I which is a view of a portion of the air speed system, including the air speed regulating valve assembly designated generally by 252. In Fig. '7 it will be seen that the operating arm 250 is rotatably mounted upon the rod 253 held by the frame 254 which is affxed to the oor I'2a of the fuselage. The cam 256 is mounted upon the arm 250 by means f the screws' 258. The air speed valve housing is designated 286 and the operating arm is numbered 283. Carried by the lower end of the operating arm 288 is the roller 29D, arranged to engage the face of cam 25B under the tension 0f spring 289 which has one end anchored to stud 289a and its other end to the arm 288. .Air speed valve 286 is in its internal construction similar to the valve shown in Fig. 6 except that this valve has no capillary nor bleed hole. The air speed regulating valve includes a port 290a. and is connected through line 294 to the step-down bellows 292 which in turn is connected to the source of vacuum 302, as shown in Fig. 3. Line 296 connects the other port 298 of the air speed valve with the bellows 300 of the air speed transmitter 284, also shown in Fig. 3. The needle within the air speed regulating valve 252 is operated by the arm 288 and this needle is positioned between the port 290 which connects with the source of vacum 302 and the seat of the valve which is connected to the other port 298 and line 296 which runs to the bellows 300 of the air speed transmitter assembly. This arrangement, it will be recalled, is similar to that shown in Fig. 6.

Referring back to Fig. 3, it has been explained that the position of link 248 may be taken as a measure of the assumed air speed. As the assumed air speed changes, the link 248 moves ahead or to the rear and the arm 250 of the air speed valve 286 is operated. The rotation of arm 250 results in a movement of cam 256, and the eccentricity of this cam results in a rotation of the operating arm 288 by coaction with roller 290. Thus the valve 286 is opened to an extent directly proportional to the assumed air speed of the trainer, and the farther open this valve becomes the greater will be the vacuum applied to the interior of the bellows 300 of the air speed transmitter 284. A suitable bleed hole '2960. is placed in the line 296 which connects the valve 252 with the bellows 300.

The construction and operation of the air speed transmitter 284 is known to the prior art and therefore a short explanation of the same will suice at this point. For a more detailed explanation, reference is made to Patent 2,465,158 granted in my name on March 22, 1949 for Aviation trainer. It will be seen that this transmitter includes a collapsible-expansible Sylphon bellows 300, and the upper end of this bellows is xed in a suitable frame member (not Shown) which is attached to the interior of the fuselage I2. To the bottom movable end of this bellows is attached a flexible link in the form of string 383 which encircles the shaft 304 and continues downward, the lower end of string 303 being attached to one end of spring 305, the other end of which is attached to the frame of the unit. The shaft 304 forms the input shafts of the two Selsyn-type transmitters 306 and 308. The housings of both transmitters 306 and 308 are mounted in the frame of the unit. The transmitter 308 is connected by the electrical cable 3I0 to the Selsyn receiver 3'II of the simulated air speed indicator 3I2. The air speed indicator 3| 2 is positioned upon the instrument panel 48 within the fuselage, as shown in Fig. 1. This indicator includes a needle 3I8 mounted upon the output shaft of receiver SII to move over the dial 320 which is graduated like the dial of the air speed indicator of a real plane. The other Selsyn-type transmitter 386 is connected by means of the electrical cable 3I4 to the Selsyn-type receiver 3I6, for a purpose soon to be described. The output shaft of this receiver is 322.

As is well known in the prior art, a collapsing of the bellows 300 as a result of an increase in the assumed air speed results in a rotation of the the contact 330 is rotated clockwise.

speed, the spring 305 causes a rotation of the` input shaft 304 in the opposite direction. The

`routput shaft of the receiver 3H associated with the instrument 3I2 will rotate through the same angle and in such a direction that the needle 3|8 moves counterclockwise to indicate a decrease in assumed air speed.

At the same time, the outputshaft 322 of the Selsyn-type receiver 3I6 isrotated'throughthe same angle as and in a direction dependent upon the direction of rotation of the input shaft 304.

It will therefore be appreciated that the indication given by the simulated air speed indicator 3I2, and that the positionl of the output shaft 322 of the Selsyn-type reoeiver3l6 is at all times in accordance with the assumed air speed of the trainer. The assumed air speed is dependent upon the combined factor of climbing or diving position of the fuselage l2, and the assumed engine power output. The assumed engine power output, in turn, depends upon the factor of throttle lever setting. The factors which affect assumed -altitude will be later ex- Reference is now made to Fig. 8 which is a detailed disclosure of the air speed unit of which the Selsyn-type receiver ,3|6 forms a part. In Fig. 8 the output shaft 322 of the receiver 3|6 is shown, and upon this output shaft is affixed the spur gear 324. The rod 32B is rigidly mounted in the frame of the unit (not shown) which is affixed to the floor of the fuselage. Rotatably mounted upon rod 326 is the gear 328 carrying the contact 330. A pair of split contact segments 332 and 334 are affixed to the insulating disc 336 which, in turn, is affixed to the gear 338 driven by the output shaft 340 of the reversible followup motor 342. Gear 338, insulating disc 336 and contact segments 332 and 334 are all mounted for rotation as a unit upon the fixed rod 326. A pair of contacts 343 and 344 are held by the frame of the unit so as to bear against the contact segments 332 and 334. Each of the spring contacts 343 and 344 is connected to the motor 342 through one of the conductors 346 or 348. Contact 330 is grounded to the frame of the unit.

Whenever an increase in the assumed air speed occurs as a result of a change in assumed engine power output or in the pitch attitude of the fuselage, the gear 324 upon the output shaft 322 of the receiver 3|6 is rotated counterclockwise, and Assuming that previous to the change in the assumed air speed, the contact 330 was in engagement with both of the contact segments 332 and 334, the motor 342 will be energized and its output shaft 3'40 will be rotated counterclockwise. Gear 338, insulating disc 336 and the contact segments 332 and 334 will be rotated clockwise, motor 342 continuing to run to rotate these elements until both of the contact segments 332 and 334are again in engagement with the contact 330. At .this point,

motor 342 will stop. As a result of the clockwise rotation of gear 338, the gear `339 which affixed upn shaft 34| which in turnis rotatably. mounted 14 in brackets held by the floor I2a of fuselage I2 will be rotated counterclockwise.

On the other hand, should a decrease in the assumed air speed occur, the gear 328 will be rotated clockwise as seen in Fig. 8. Contact 330 will be rotated counterclockwise and will then engage only the contact segment 332. Motor 342 will be energized to rotate its output shaft 4340 clockwise and the gear 338, insulating disc v336 and contact segments 332 and 334 will all be rotated counterclockwise until the segments 332 and 334 again are in engagement with contact -330. At this instant, motor 342 will stop. The.

counterclockwise rotation of gear 338 will result in a, clockwise rotation of the gear 339.

Consequently, the statement may be made that the gear 339 is rotated counterclockwise in response to an increase in the assumed air speed and that the angle through which this gear is so rotated is proportional to the magnitude of the change in air speed. Also, gear 339 is rotated clockwise in response to a decrease in assumed aid speed and the angle through which it is so rotated is proportional to the magnitude of the change in assumed air speed. Accordingly, the gear '339 is always positioned in rotation from a predetermined initial point according to the instant assumed air speed, so the position of this gear may be taken as a measure of the instant assumed air speed.

Shaft 34| will be rotated with gear 338, as will arm 350 which is affixed upon shaft 34|, and to the lower end of which is affixed the forward end of link 352. As seen in Fig. 3, the rear end of link 352 is pivotally attached to the upper end of arm 354, the lower end of which is rotatably vmounted upon rod 364. Link 358 has its forward end pivotally attached to the arm 354. It will be appreciated that the link 358 of Fig. 3 is moved tc the rear as a result of an increase in assumed air speed, and is moved to the left as a result of a decrease in assumed air speed. Accordingly, the position of this link is at all times dependent upon the factor of assumed air speed.

Combining the factor of assumed air speed and pitch attitude to produce assumed vertical speed It has previously been explained that whenever the fuselage I2 is dived, the sector 218 is rotated clockwise as seen in Fig. 3, resulting in a similar rotation of the shaft 280 and of the arm 246 which is aixed upon the left end of this shaft. As best seen in Fig. 9, the rod 244 is carried by arm 246, the outer end of this rod passing through the fork 245 in the upper end of arm 360, the lower end of which arm is aixed upon the rod 352, the other end of this rod being carried by the lower end of arm 245. It will therefore be appreciated that the arm 3'60 is always rotated the same direction and through the same angle as is the arm 246 which is carried by shaft 280. Arm 360 carries the stud 364, upon the outer end of which is pivotally mounted the arm 354. As previously explained, the forward end of link 358 is pivotally connected to arm 354.

Accordingly, when the lower end of arm` 246 moves ahead in response to a diving of the fuselage, the lower end of arm 360 moves in the same direction, as does stud 364. The lower end of arm 354 also moves ahead, this arm pivoting about the point at which link 352 is attached thereto. .Link 358 also moves ahead. Accordingly, link 358 moves ahead in response to a diving of the fuselage. It has previously been pointed outthat 15 this link also moves ahead in response to a decrease in assumed air speed.

On the other hand, it will be understood without a detailed explanation that whenever the trainer fuselage assumes a climbing position, by means of shaft 280 and the apparatus disclosed in Fig. 9, the link 358 will be moved to the rear. Accordingly, link 358 is moved to the rear in response to an increase in assumed air speed. As previously explained, it moves in the same direction in response to a raising of the nose of the fuselage.

It will be appreciated that in real aircraft the vertical speed of the plane depends upon the combined factors of plane attitude and air speed. An increase in air speed and a raising of the nose of the plane results in an algebraic increase in vertical speed, While a decrease in airspeed and a nosing down of the plane results in an algebraic decrease in vertical speed. (As used hereinafter, the term algebraic increase means a decrease in rate of descent, changing descent to ascent, changing a vertical speed of zero to ascent, or increasing a rate of ascent. Algebraic decrease means a decrease in rate of ascent, changing ascent to descent, changing a vertical speed of zero to descent, or increasing rate of descent.) Inasmuch as link 358 moves ahead in response to a diving of the fuselage and in response to a decrease in assumed air speed, and moves toward the rear in response to a raising of the nose of the fuselage and to an increase in assumed air speed, it will be appreciated that the position of link 358 at any instant may be taken as a measure of the factor of assumed vertical speed. When the factor of assumed vertical speed is algebraically increased, link 358 moves to the rear, and when the factor of assumed vertical speed is algebraically decreased, link 35B moves ahead.

Referring back to Fig. 3, it will be seen that the rear end of link 358 is pivotally attached to the outer end of arm 366 which together with the arm 368 forms a bellcrank arrangement, the bellcrank being pivotally held by the outer end of block 310, which together with the arm 314 forms a second bellcrank pivotally mounted upon the pin 312 which is integral with the bracket 316 which may be affixed to the floor of the fuselage. Integral with bracket 316 is the extension 318 which holds one end of the tension spring 380, the other end of which is held by the outer end of the bellcrank arm 314. The left end of link 382 is pivotally attached to the outer end of the bellcrank arm 368, and the right end of this link is attached to the lever 384 which is pivotally mounted upon the pin 386 carried by the xed vertical wall 388 which is integral with the base member 390 which may be affixed to the floor of the fuselage. The other end of lever 384 has pivotally connected thereto the left end of link 392, the right end of which is pivotally connected to the rear end of lever 394 which in turn is pivotally mounted upon the pin 396 carried by the central bellows member 398, which member for present purposes may be considered to be stationary. The forward end of lever 394 carries the pin 400, the upper end of which is aiixed to the sleeve 402 which encircles link 406. The left end of link 406 carries a fixed stop 408 and the compression spring 410 encircles link 406, the left end of this spring bearing against stop 408 and the other end bearing against the left end of sleeve 402. Link 406 carries a second stop 4I2 and a second compression spring 4|,4 encircles link .406, the

right end of this spring bearing against stop 4|2 and the left end of the spring bearing against the right end of sleeve 402. As is well known, a sleeve 419 may be placed inside sleeve 402, sleeve 4|9 being aixed upon link 406.

It will be appreciated that the arrangement just disclosed is a conventional compensating arrangement, the exact purpose of which will later become more apparent.

Referring now to Fig. 10, the link 406 is shown, and it will be seen that its right end is pivotally attached to the rear end of arm 4|6 which is afxed to the lever 4|8, lever 418 being pivotally mounted upon the pin 420 which may be suitably affixed to any fixed part of the trainer fuselage. The link 422 has its fore end pivotally attached to the left end of lever 4|8, the rear end of this link being pivotally attached to the upper arm of bellcrank 424 which may be arranged to pivot about the point 426. The other end of bellcrank 424 is pivotally attached to the yoke 428 by means of pin 430, yoke 428 being affixed upon the upper end of plunger 432 of the dashpot 434.

Pivotally attached to the right end of lever 4I8 is the link 436, the rear end of which is aixed to the block 438 which is slidably mounted upon the rod -440 which may be xedly held by a suitable frame member which in turn is attached to the fuselage. A pair of stops 442 and 444 may be aixed upon the rod 440 for a purpose to be later described.

When the link 358 moves to the rear in response to an algebraic increase in the factor of assumed vertical speed, the outer end of arm 366 moves in the same direction and the rear end of arm 368 moves toward the right. The reversing lever 384 is moved, resulting in a movement to the left of link 392, and the response of the reversing lever 394 to this movement of link 392 results in a movement to the right of the pin 400 and sleeve 402. The compensating arrangement will transfer the motion of pin 400 to the link 406, and link 406 will also move toward the right.

Referring to Fig. l0, the movement to the right of link 406 will result in a counterclockwise rotation of lever 4 I 8, as seen from above, link 422 moving to the rear and link 436 moving ahead. The dashpot 434 in conjunction with the compensating spring arrangement will delay the movements of link 422. The forward movement of link 436 results in a similar movement of block 438 along rod 440.

On the other hand, whenever link 358 is moved ahead in response to an algebraic decrease in the factor of assumed vertical speed, it will be appreciated that all of the parts shown in Figs. 3 and 10 which have just been described as being responsive thereto will move in the opposite direction from that just explained, and the block 438 in Fig. 10 will move toward the rear. Accordingly, the position of block 438 along rod 448 may be taken as a measure of the factor of instantl assumed vertical speedthe farther ahead this block is positioned, the higher algebraically is the factor of assumed Vertical speed.

Still referring to Fig. 10, it will be seen that the block 438 has formed integrally therewith the rack 446 having teeth 448 which are aligned with the teeth 448 integral with the under side of block 438. The pinion 458 which is affixed upon the shaft 452 is driven by the teeth 448, and upon the may be mounted in any suitable manner.

pin 456 engages the slot 458 in the disc 460 which is afiixed upon the rotor 462 of the vertical speed Selsyn transmitter 464 which is connected through cable 466 to the Selsyn receiver 468, upon the output shaft of which is mounted the needle 410 which moves over the dial 412 which is graduated to have the appearance of the vertical speed indicator of a real plane. The Selsyn receiver 468, needle 410 and dial 412 form the vertical speed indicator designated generally by 414. The indicator 414 is positioned upon the instrument panel as shown in Fig. 1.

Still referring to Fig. 10, a boss 416 is carried by the Selsyn transmitter 464, and this transmitter may be mounted in any suitable frame member. A hair spring 418 is provided, the outer end of this spring being aiiixed to the boss 416 and the inner end aixed to rotor 462 so as to constantly bias the rotor 462 and disc 460 in the clockwise direction, in order to eliminate any play between the pin 456 and slot 458.

It will be noted that the axis of shaft 462 is offset from the axis of shaft 452 by a predetermined amount.

In view of the just disclosed arrangement, it will be appreciated that when the rack 446 moves toward the head of the fuselage in response to an algebraic increase in assumed Vertical speed, the pinion 450, shaft 452, disc 454, pin 456, disc 460 and rotor 462 will all be rotated counterclockwise. The electrical connection between the Selsyn transmitter 464 and Selsyn receiver 466 may be made such that the needle 410 is rotated clockwise over the face of dial 412 to indicate an algebraically greater assumed vertical speed. On the other hand, when block 438 is moved toward the rear in response to a decrease in assumed vertical speed, the just described parts are moved in the opposite directions, resulting in a counterclockwise movement of needle 410 relative to dial 412, thereby indicating an algebraically lower assumed vertical speed.

It will be appreciated that the dash-pot 434 in Fig. and compensating spring arrangement shown in Fig. 3 will delay the movements of the input link 406 of the altitude unit so the changes in the readings of the vertical speed indicator 414 properly lag changes in the pitch attitude of the fuselage and changes in the operation of the air speed system. Thus, when the trainer fuselage is nosed down so that indicator 414 indicates a rapid rate of descent, when the nose of the fuselage is pulled up into a climbing position the vertical speed indicator may for a predetermined length of time indicate a gradually decreasing rate of descent, and then a gradually increasing rate of ascent.

The opposite would be true in changing the attitude of the fuselage from nose-up" to nosedown. Thus, the apparatus closely simulates the operation of a real vertical speed indicator ina plane in actual flight under corresponding flight conditions.

In Fig. l0 it will be appreciatedr that the shaft 452 which controls the readings of the indicator 414 moves linearly in response to changes in assumed vertical speedi. e., for any change of a given magnitude in the factor of assumed vertical speed, shaft 452 always rotates through the same angle. Referring to Fig. 11, it will be noted that the dial 412 of the Vertical speed indicator 414 is not graduated linearly, but is instead graduated logarithmically. At relatively low assumed vertical speeds, the needle 410 moves through a larger angle for a change of given magnitude in assumed vertical speed than is the case at higher assumed vertical speeds. The same is also true of the needle of a vertical speed indicator in a real plane. Accordingly, referring to Fig. 10, if the shaft 452 were directly coupled to the shaft 462 it will be appreciated that the two shafts would move linearly with respect to one another, and that the needle 410 would always move through a given angle for a given magnitude of change in assumed vertical speed, regardless of whether the change occurred at a relatively high or relatively low assumed vertical speed. Obviously, the indicator 414 would not indicate correct assumed vertical speeds.I

In order to avoid such incorrect indications, the rotor 462 of transmitter 464 is axially displaced from the shaft 452, and the coupling including disc 454, pin 456 and'disc 460 having slot 458 is employed. The apparatus shown in Fig, 10 may be initially adjusted so that when assumed Vertical speed is zero, the slot 458 is in a horizontal' position. The pin 456 will then be relatively close to the axis of rotor 462. The .indicator 414 may then be arranged to indicate an assumed vertical speed of zero. Thereafter, when shaft 452 begins to rotate as a result lof a change from an assumed vertical speed of Zero, at first the rotation of pin 456 acting upon the disc V460 will result in a larger angular movement of the rotor 462 than the angular movement of shaft 452. Accordingly; needle 410 moves across the dial 412 in Fig. 11` through a larger angle than shaft 452 is rotated; However as shaft 452 continues to rotate, the angular rotation of shaft 462 becomes gradually less in response to any given angular movement of shaft 452, until the angular movement of shaft 462 in response to the angular movement of shaft 452 becomes actually less than the angular movement of shaft 452. Accordingly, even though the movement of shaft 452 is linear in proportion-to changes in assumed vertical speed, the angular movement of needle 410 is logarithmic in relation to the movement of shaft 452, and the correct assumed vertical speed may be obtained by reference to the indicator 414.

Means for integrating assumed vertical speed and time to produce assumed altitude Referring again to Fig. 10, it will be seen that a constant speed motor 480 is provided to drive, by means of the reduction gear train contained in housing 482, the shaft 484 upon the outer end of which is aixed the hub 486 integral with the disc 488 upon the face of which is affixed the rubber disc 490. Set screw 492 may be employed to a'ix hub 486 upon shaft 484. The motor 480 may be carried by housing 482 which in turn is axed to the casting 496 by means of screws 494. Casting 496 is pivotally held by a pair of pins 498 (only one shown) which in turn are held by the brackets 500 which may be xedly carried by a suitable frame member. The member 496 carries a pair of pins 502 upon each of which is rotatably mounted a roller 504. A pair of springs 506 have their left ends attached to the pivotally mounted casting 496 at points above the axes of pins 498, and the other end of each of the springs 506 may be suitably attached to any fixed member.

A splined shaft 508 is provided, and this shaft may be mounted for rotation in any suitable manner. Upon this shaft is positioned the interiorly splined driven wheel 510,Y preferably made of brass, to which is affixed the grooved hub 5I2. A yoke 5 I4 integral with block 438 fits in the groove of hub 512, and it will be appreciated that reciprocation of block 438 in response to changes in assumed vertical speed will result in a movement of hub 512 and Wheel |0 along the splined shaft 508. It will also be appreciated that the springs 506 exert a force upon the casting 496 and rollers 504 which in turn thrusts the rubber driving disc 490 against the driven Wheel 510 to prevent slippage between the rubber driving disc 490 and the driven wheel 5|0.

A conventional type diierential designated generally by 516 is provided, this differential including the frame 518, the primary input gear 520, the output gear 5-22, and the two idler gears 524. The secondary input is in the form of the spur gear 526 which is aixed upon the frame 518. The rear end of spline 508 has axed upon its rearmost end the primary input gear 520. Gear 526 and frame 518 are free to rotate relative to the said end of spline 508. The output gear 522 of differential 516 is axed upon the forward end of rotor 528 of the Selsyn-type altitude transmitter 530. Transmitter 530 is connected through the electrical cable 532 with the Selsyn receiver 534, the output shaft of which controls the position of the needles 536 which move over the dial 538 which is graduated like the altimeter of a real plane. Receiver 534, needles 536 and dial 538 form the altimeter designated generally by 540. This altimeter is located upon the instrument panel 48, as shown in Fig. 1.

Afxed upon shaft 528 is the bevel gear 542 which drives the bevel gear 544 and the other gears 546, 548, 550, and 552 of the reduction gear train designated generally by 554. Gear 552 is affixed upon shaft 556, upon the right end of which is aiiixed the arm 558, to the upper end of which is pivotally attached the rear end of link 560, the forward end of which is attached to the upper end of the previously mentioned arm 196, shown in Fig. 3.

In Fig. 10, a second constant speed motor 562 is provided, and this motor through the reduction gear train contained in housing 564 drives the routput shaft 566 upon which is affixed the spur gear 568 which in turn drives the gear 526 which forms the secondary input of differential 516.

Also upon the shaft 556 are affixed the tWo cams 510 and 512 which respectively engage, under conditions to be later more fully described, the rollers 514 and 516 respectively carried by the movable contacts 518 and 580 of the microswitches 582 and 584 which may be suitably fixed in position.

In adjusting the previously described apparatus for operation, the block 438 and yoke 514 may be adjusted so that when assumed vertical speed is zero the driven wheel 510 bears against disc 490 half-way between the center of disc 490 and the rear edge of this disc, as shown in Fig. 10. As previously explained, under this assumed condition the slot 458 in disc 450 is in the horizontal position, also as shown.

The apparatus shown in Fig. 70 may be designed so that the motor 480 drives the disc 490 at a constant rate in the counterclockwise direction as seen from the left. The motor 562 may drive the gear 568 clockwise as seen from the front at a constant speed. In adjusting the apparatus under the condition of an assumed vertical speed of zero, the block 438, yoke 514 and driven Wheel 510 are positioned so that the wheel 510 is driven counterclockwse as seen from the front at the exact rate necessary to cancel the input of differential 516 resulting from the rotation of gear 568 and the counterclockwise rotation of gear 526 and frame 518 of differential 516. Accordingly, the output shaft 528 of differential 516 which also forms the rotor of transmitter 530 remains stationary under the condition of an assumed vertical speed of Zero, and the assumed altitude indicated by indicator 540 remains constant. At the same time, the vertical speed indicator 414 is adjusted to indicate an assumed vertical speed of zero. Thereafter, when the previously described controlling factors result in an algebraic increase in assumed vertical speed, the link 436 and block 438 move ahead, resulting in a movement of the driven wheel 510 toward the center of the rubber driving disc 490. The speed of rotation of Wheel 510 will decrease, as will the rotation of spline 508, but inasmuch as the secondary input of differential 516 remains constant the output shaft 528 will be rotated counterclockvvise at a rate dependent upon the magnitude of the assumed positive Vertical speed. At the same time, as previously explained, the shaft 452 will be rotated so that the vertical speed indicator 414 will indicate the correct assumed vertical speed.

On the other hand, should the link 436 and block 438 move to the rear in response to an algebraic decrease in the factor of assumed vertical speed, the driven wheel 510 will be moved toward the periphery of the driving disc 490, and the rate of rotation of this wheel as well as that of the spline 508 will be increased. The primary input of differential 516 will therefore exceed the constant secondary input, and the output shaft 528 which also forms the rotor of transmitter 530 will be rotated clockwise as seen from ahead. The altimeter 534 will have its indication changed to indicate a lower altitude, and the vertical speed indicator 414 will indicate an algebraically decreased assumed vertical speed.

It will be appreciated that the direction of turning of the output shaft 528 depends upon whether the assumed vertical speed is positive or negative, and that the rate of turning of the shaft depends upon the instant assumed magnitude of the vertical speed. The duration of any given direction and speed of rotation of shaft 528 prevails as long as the assumed vertical speed remains constant, and no longer. Accordingly, the apparatus of Fig. 10 integrates assumed vertical speed With time, and the angular positon of shaft 528 from the predetermined zero altitude position at any instant is a proper measure of the assumed altitude of the trainer.

In Fig. 10 the stop 442 is provided so that the block 438 which positions the driven wheel 510 cannot move ahead sufficiently far to move the driven wheel 510 ahead of the center of driving disc 490. At the same time, stop 444 is provided so that the driven wheel 510 cannot be moved beyond the periphery of the driving disc.

Reference is now made to Fig. 12 which is a wiring diagram showing the electrical circuits of the motors 480 and 562, as well as the relationship of the micro-switches 582 and 584 to these motors. In Fig. 12 the conductor 600 is connected to one side of the volt source, and this conductor is directly connected to the field coil of motor 480 and is connected to the field coil of motor 562 through the conductor 602. The other side of the coil of motor 480 is connected through the microswitch 582 and conductor 604 with the sa-asco www switch 606, the rotor of which is designated 606a and is connected through conductor 608 to the other side of the 110 volt source through the trainer ignition switch 609. The other side of the coil of motor 562 is connected through the microswitch 584 and conductor 6I0 to one side of switch 6I2, the rotor of which is designated 612a and is connected by means of conductors 6I4 and 608 and switch 609 to the other side of the 110 Volt source. The switches 606 and 612 in reality are a. two-gang switch having three terminals up, off and down. A single manual control 6I6 controls both of the rotors 606m and 6I2a. In normal operation the manual control 6I6 is in its neutral position'so that the rotors 60611 and 6|2a engage the off terminals of the switches. With the manual control 6l6 so positioned, and assuming that the trainer is in normal operation, when the shaft 528 which forms the rotor of the altitude transmitter 530 reaches such a position that the altimeter 540 indicates an assumed altitude of 20,000 feet, or any other selected altitude, the cam 512 affixed upon shaft 556 which is controlled by the shaft 528 engages the roller 516 upon the movable arm 580 of the micro-switch 584, causing this micro-switch to open. Referring to Fig. 12, it will be seen that the opening of the micro-switch 584 will result in a de-energization of motor 562. However, motor 480 will continue to run. Referring to Fig. 10, the stopping of motor 562 will suspend the operation of the secondary input of differential l6, but the continuing rotation of the constant speed disc 490 and of the driven wheel 5I0 will result in a clockwise rotation of shaft 528, as seen from ahead, in which direction shaft 528 rotates to decrease assumed altitude. The altimeter 534 will begin to rotate to indicate a lower assumed altitude, and through the gear train 554 the shaft 556 will be rotated clockwise, closing the micro-switch 580, again rendering motor 562 operable. As soon as the assumed altitude again reaches 20,000 feet-which may be in a few seconds, depending upon the assumed vertical speedthe process will be repeated upon the opening of switch 584 by cam 512. It will therefore be appreciated that the cam 512 and microswitch 584 limit the assumed altitude at which the trainer may be flown, thus simulating the reaching of the ceiling of an aircraft, and also limiting the angular movement of shaft 556 so that the link 560 will not be moved sufficiently far to damage the valve |84 in Fig. 3.

During the use of the trainer for the instruction of students in the art of instrument flight, as the assumed altitude approaches and reaches zero, the shaft 556 is positioned so that the cam 510 carried thereby engages the roller 514 carried by the movable contact 518, thereby opening the limit switch 582. Referring to Fig. 12, when the limit switch 582 is opened it will be appreciated that the motor 480 is de-energized, but the motor 562 continues to run. The primary input of differential 5l6 in Fig. 10 will be suspended, and the running of motor 562 will result in a counterclockwise rotation of shaft 528 as seen from ahead-the same direction in which it is reached to increase assumed altitude. The altimeter 534 will show an increase in altitude, but almost immediately the shaft 556 will be rotated counterclockwise to disengage cam 510 from roller 514, and switch 582 will be closed, reenergizing the motor 480. As soon as assumed altitude again reaches zero-which may be in a few seconds, depending upon assumed vertical speed-the process will be repeated. Accordingly, it is impossible for the altimeter 540 to indicate an assumed altiude of below zero.

If for any reason during adjustment or testing of the apparatus it is desired to go quickly from a relatively low to a relatively high assumed altitude, the manual control 6I6 of Fig. l2 is placed in the up position, and it will be seen in Fig. 12 that such a positioning of control 6I6 will result in a de-energization of the. disc drive motor 480. Accordingly, motor 562 is the only motor operating into the differential 5l6, and the altimeter 534 may be made to show a high altitude in a relatively short length of time. At the same time, shaft 556 and the link 560 controlled thereby will be rapidly rotated into a high assumed altitude position.

On the other hand, with the apparatus positioned in a relatively high assumed altitude position, when it is desired to quickly position the apparatus in a. relatively low assumed altitude position, the manual control 616 is placed in the down position, and it will be noted in Fig. 12 that such a positioning of control 6 I 6 disconnects the differential drive motor 562 from the 110 volt source. Accordingly, only the primary of differential 5l6 is operated, and the rotor 528 of the altitude transmitter 530 is rotated clockwise as seen from the front, and the altimeter 534 indicates a rapid loss of altitude. Shaft 556, of course, assumes a correspondingly low altitude position.

In view of the preceding explanation, it will be appreciated that the link 560 shown in Figs. 3 and 10 is always positioned fore and aft of the trainer` fuselage according to the instant assumed altitude, the higher the assumed altitude, the farther ahead the link 560 will be placed. It will be recalled that the farther ahead link 560 is placed the greater will valve |84l be opened, and consequently the greater will be kthe vacuum applied to the Sylphon bellows 222 of Fig. 3. As previously explained, an application of increased vacuum to this bellows results in a greater collapsing thereof, and by means of the amplifier designated generally by H8, the lassumed manifold pressure indication will be decreased, and the link 240 is moved ahead. Such a movement of link 240 affects the airspeed system, as previously described, and results in a lower indicated assumed airspeed. At the same time, the lower assumed airspeed results in a movement ahead of the link 358, which link is positioned according to the instant assumed vertical speed--this link being moved ahead in response to a lower assumed vertical speed. The input of the altitude and vertical speed unit shown in Fig. 10 will therefore be affected, as previously described, in response to the decrease in assumed airspeed, to indicate an algebraically lower assumed vertical speed, and altitude will be properly affected. On the other hand, should the link 560 move in the opposite direction in response to a decrease in assumed altitude, the same ap paratus will respond except its direction of movement will be reversed, and higher assumed manifold pressure and air speed indications will result, as will an algebraically higher assumed vertical speed. The altitude indication will respond properly to the change in assumed vertical speed.

Accordingly changes in assumed altitude affect the assumed manifold pressure indication, assumed air speed indication, as well as the assumed vertical speed and assumed altitude indications.

n View of the preceding disclosure it will be appreciated that this invention discloses a completely new form of altitude system for use in grounded aviation trainers, and that this new apparatus has many important advantages over the previously used pneumatic system. It is possible to achieve as high an assumed altitude as is desired, and a very sensitive system is produced, especially near the zero vertical speed position. This is achieved by reason of the fact that the spline 568 and gear 526 always rotate in the same direction, thereby eliminating backlash in going from a positive to a negative assumed vertical speed. It is not necessary to graduate each vertical speed indicator and altimeter separately because the responses of the mechanical apparatus to the governing mechanical movements may be accurately predicted in the designing of the apparatus.

It is also possible, with the apparatus of this invention, to obtain an assumed altitude of any desired amount.

It should be particularly noted that many of the advantages of this invention may be achieved by the use of a single motor which may drive both the constant speed disc and the secondary differential input in Fig. 10. Two motors are necessary only to achieve the previously described advantages of quickly changing from a high assumed altitude to a low assumed altitude, or vice versa.

Rough air mechanism Reference is now made to Fig. 1 where the general positioning of the rough air mechanism of this apparatus is shown, the apparatus being designated generally by 625. In Fig. 13 it will be seen that the same unit is shown in perspective form, and is designated by the same reference character. This unit includes a base 626 which may be suitably aiixed within the fuselage l2. A pair of upright brackets 628 are in turn affixed to the base 626. These two brackets hold a rod 630 upon which are rotatably mounted a plurality of cams designated 632, 634, 636, 638, 640, 642, 644, 646, 648 and 650. Also a pair of gears 652 and 654 are freely mounted upon the rod 630. The gear 652 has a predetermined number of teeth, e. g., 19, while the gear 654 has a slightly diierent predetermined number of teeth, e. g., 80. Gear 652 and the cams 632, 634, 636, 638, 640, 642, 644 and 646 are pinned together by the pin 656 in order that they will rotate as a unit upon the rod 638. At the same time, the gear 654 and the two cams 648 and 650 are pinned together by pin 658 in order that they will rotate as a unit relative to the rod 630. A gear 660 may be rotatably mounted upon the rod 662 which is held in any desired manner, this gear being driven by the pinion 664 which in turn is driven by the synchronous motor 666. Motor 666 may be energized and de-energized by the main ignition switch in the trainer, which switch, being well known, is not disclosed at this point. It will therefore be appreciated that upon closing of the ignition switch the two gears 652 and 654 and the cams pinned thereto rotate about the rod 630, gear 652 and the cams pinned thereto rotating at a slightly greater rate than the gear 654 and the cams pinned to that gear. The apparatus may -be designed to rotate the cams at a slow rate, e. g., one R. P. M.

It will be noted that each of the cams has a plurality of alternating peripheral projections 668 and depressions 610, and that insofar as the cam 632 is concerned, some of its depressions 616 are deeper than others. The purpose of the projections and depressions of these cams will be later described.

The rough air unit designated generally by 625 includes a main manifold which in turn includes a back member 612, a middle member 614 and a front member 616. Fig. 14 is an end view of these three members showing them in their relative positions. The rear member 612 includes a vertically disposed member 618, the face of which as seen in Fig. 15 is perfectly flat, except for the screw holes 686 therein. Integral with member 618 is the horizontally disposed support 680, and three vertical strengthening members 682 are integrally formed with members 618 and 680.

A slot 684 is placed in the left-most member 682.-

Integrally formed with the rear edge of the horizontal member 680 are a plurality of bosses 688, each of which is drilled at 690 for the reception of rod 692.

Reference is now made to Figs. 16 and 17 which are rear and front views of the intermediate manifold member 614. In Fig. 16 which is a view of the rear side of member 614, it will be seen that the rear side is perfectly flat except for the two horizontal channels 694 and 696 placed therein. These channels do not extend completely through member 614. A plurality of ports 698, 100, 102, 104, 106, 108, and 1l0 pass through the front face of member 614 and communicate with lower channel 694. At the same time, a plurality of ports 112, 114, 1I6, 1|8, 120, 122, 124, 126, and 128 pass through the front face of member 614 and communicate with the upper channel 696 in the rear side thereof. In Fig. 17 it will be seen that the front face of member 614 has a plurality of vertical recessions therein, equal in depth to the thickness of the slide valves 130, 132, 134, 136, 138, 140, 142, 146 and 148, so that the front surfaces of the slide valves and the intermediate portions of the front face of the member 614 form a continuous flat surface except for the ports in the slide Valves.

It will be noted that the slide valve 130 has two ports 152 and 154 passing therethrough; the slide valve 132 has two ports 156 and 158 passing therethrough; and the slide valve 134 has two ports and 162 passing therethrough. The ports in valve 132 are intermediate in size with respect to the ports in valves 130 and 134.

The Valve 136 has a single port 164, and valve 138 has a single port 166. The valve 140 has two ports 168 and 110; valve 142 has two ports 112 and 114; valve 146 has two ports 116 and 118; and valve 148 has two ports 180 and 182. All of the ports in all of the valves pass completely through the valves, and when the valves are in their downmost position as shown in Fig. 17, the ports therein are arranged with respect to the ports in the member 614 as shown.

A plurality of screw holes 184 pass through the member 614 and are aligned with the screw holes 686 in the rear member 612.

The rear face of the front member 616 is perfectly flat except for the two channels 186 and 188 therein, the screw holes passing therethrough, and the ports 192, 194, 196, 198, 800, 802, 804, 806, 808, and 8|0 passing therethrough. When the screws SI2, seen in Fig. 14, hold the three members 612, 614, and 616 in assembled position, the channel 186 in the rear face of the front member 616 lies opposite the three ports 102, 100, and 698 in the center member 614; the channel 188 lies opposite the ports 1|2, 1l4 and 116 in mem- 25 ber 614; port 192 lies opposite port 118 and port 194 lies opposite port 120 in member 614; ports 196, 198, 800 and 802 respectively lie opposite the ports 104, 122, 106, and 124 in member 614; and ports 804, 806, 808 and 810 are respectively opposite ports 108, 126, 110 and 128 in member 614.

However, when the slide valves are positioned as shown in Fig. 17, it will be appreciated that none of the ports nor the counterbores in member 616 are in communication with any of the ports in the intermediate member 614.

In Fig. 18 it will be seen that the port 814 passes through the front face of member 616 and communicates with the channel 186, while the port 816 similarly passes through the front face of member 616 and communicates with channel 188. Referring to Fig. 13 it will be seen that the port 8 I4 opens into the atmosphere, and it will therefore be appreciated that the channel 186 is at all times at atmospheric pressure. A coupling 8 I 8 is inserted in the port 816, and a suitable pneumatic line 820 has one end connected to coupling 818 and its other end to a suitable source of vacuum 822. Accordingly, channel 188 is at all times at a predetermined reduced pressure potential.

In Fig. 13 it will be seen that a coupling 824 is inserted in the port 192, and hose 824a is connected to coupling 824, the other end of hose 824a being shown in Fig. 3 connected to the coupling 825 carriedfby the fixed vertical member 388. A bleed hole 824b is placed in line 824a. The member 388, movable member 398 and cloth covering 86 form an air-tight bellows designated generally by 811. A couping 826, as seen in Fig. 13, is placed in port 194 and one-end of pneumatic line 82641 connects to the outer end of this coupling. In Fig. 3 it will be seen that the other end of pneumatic line 826a is connected to the coupling 821 which is carried by the xed vertical member 388a. Bleed hole 82617 is placed in line 826er. The member 388a, movable member 398 and cloth covering 88 form a second air-tight bellows designated generally by 82. In Fig. 13 coupling 828 is shown in communication with port` 198, and one end of pneumatic line 828a is connected to coupling 828. In Fig. 1 it will be seen that the other end of pneumatic line 82811, is connected to the left banking bellows 34. In Fig. 13 it will be seen that the coupling 830 is in communication with port 802, and that one end of pneumatic line 8301l is connected to coupling 830. In Fig. 1 it will be seen that the other end of pneumatic line 830a is connected to the right banking bellows 36. i

Also in Fig. 13 it will be seen that the port 196 isconnected through the coupling 83| with the coupling 830, and that port 800 is connected through coupling 833 with the coupling 828. Coupling 832 has one end inserted in port 806, and the other end of this coupling is connected by pneumatic line 832a with the forward pitching bellows 30, as shown in Fig. 1. At the same time, coupling 834 is inserted in port 810, and pneumatic line 834a connects this coupling with the rear pitching bellows 32, also as seen in Fig. 1. In Fig. 13 it will be seen that connector 835 connects port 804 with coupling 834, and that cou pling 836 connects port 808 with the coupling 832.

In Fig. 14 it will be seen that there are provided a plurality of .rockers designated by the numbers 850, 852, 854, 856, 858, 860, 862, 864, and 866, each of these rockers extending substantially vertically, but slightly inclined to the rear. Integral with each of the just mentioned rockers is the long extension bearing the same numbers with the suix a added. The rocker 850 together with its integral extension 850a, is shown in Fig 19, and it will be seen that this rocker has a pair of upstanding lugs 8501) in each of which is drilled a hole 850e for the reception of the pivot rod 692. Each of the rockers is identical in construction. In Fig. 13 it will be seen that the foremost end of the extension of each of the rockers passes through the rectangular slot in the uppermost end of each of the nine vertical slide valves. Each of the nine rockers is disposed in vertical alignment below a diierent one of the nine cams shown in Fig. 13 to the right of cam 632. As seen in Fig. 19, a hole 850d is drilled in the horizontal extension 850a of rocker 850, and a corresponding hole 850e is drilled in the top of the rear manifold member 612. A hairspring 850f is provided, one end of this spring being inserted through the hole 8500i, the spring encircling rod 692, and the other end of this spring being inserted through the hole 850e. It will be appreciated that the hairspring 850i will return the extension 850a of rocker 850 to the position shown in Fig. 13. Each of the rockers and rocker extensions has a similar spring arrangement to that shown in Fig. 19.

Referring again to Fig. 13, it will be seen that the rough air control knob is designated 900 and is aixed upon the outer end of the shaft 902 which is rotatably supported by the left bracket 628. A collar 904 is integral with the inner end of shaft 982, and an eccentric pin 906 having its axis displaced from the axis of shaft 902 is integrally formed with collar 904. Pin 906 passes through the slot 684 in the left end of manifold member 612. The rod 908 is ixedly carried by left bracket 628, and upon the right end of this rod is rotatably mounted the hub 910 which is aflixed to the front end of the arm 912 which carries the roller 914, the other end of arm 912 engaging the top of the compression spring 916 which in turn is supported by the member 918 which is attached to base 626. The rear end of arm 912 may be aixed to the lower end 920a of the collapsible-expansible metallic bellows 920 which is supported by means of bracket 922 and nut 923. A pneumatic line 924 connects the bellows 920 with the pneumatic line 296 of the airspeed system, as shown in Fig. 3. Except for the connection with pneumatic line 924, bellows 920 is air-tight.

Referring back to Fig. 13, the arm 926 has its lower end movably mounted upon the eccentric pin 906, and the upper end of this arm has a Vertical slot 928. A pin 930 is carried by the arm 912 and is positioned in slot 928. A pair of pins 932 (only one shown) are provided, each of these pins being xedly mounted in axial alignment in a different one of the brackets 628, and each. of these pins enters a block 934 (only one shown), each of which blocks is attached to opposite ends of the middle manifold member 614. The manifold members 612, 614 and 616 are free to pivot about the axes of pins 932 in a manner which will be later described.

Considering now the operation of the rough air apparatus, when the rough air control handle 900 is positioned as shown in Fig..13, the manifold members and the rocker arms 850-866 are positioned so that when the cams are rotated their peripheries do not engage the vertically extending rockers. Accordingly, the entire apparatus is rendered inoperative.

However, assuming that the control handle 900 78 is rotated clockwise a predetermined distance, it 

